An aerial view of the 1933 Century of Progress Exhibition, which includes the sky ride in the background, before it opened in 1933 on the lake front in Chicago. The fair attracted more than 40 million visitors.

An aerial view of the 1933 Century of Progress Exhibition, which includes the sky ride in the background, before it opened in 1933 on the lake front in Chicago. The fair attracted more than 40 million visitors. (Tribune archive photo)